Synthetic and X-ray diffraction studies of borosiloxane cages [R′Si(ORBO)3SiR′] and the adducts of [ButSi{O(PhB)O}3SiBut] with pyridine or N,N,N′,N′-tetramethylethylenediamine

Article abstract of DOI:10.1016/j.poly.2006.12.045

Eleven borosiloxane [R′Si(ORBO)₃SiR′] compounds where R′ = Bu^t and R = Ph (1), 4-PhC₆H₄ (2), 4-Bu^tC₆H₄ (3), 3-NO₂C₆H₄ (4), 4-CH(O)C₆H₄ (5), CpFeC₅H₄ (6), 4-C(O)CH₃C₆H₄ (7), 4-ClC₆H₄ (8), 2,4-F₂C₆H₃ (9), and R′ = cyclo-C₆H₁₁ and R = Ph (10), and 4-BrC₆H₄ (11) have been synthesized and characterized by spectroscopic (IR, NMR), mass spectrometric and, for compounds where R′ = Bu^t and R = 4-PhC₆H₄ (2), 4-Bu^tC₆H₄ (3), 3-NO₂C₆H₄ (4), CpFeC₅H₄ (6) and 2,4-F₂C₆H₃ (9), X-ray diffraction studies. These compounds contain trigonal planar RBO₂ and tetrahedral R′SiO₃ units located around 11-atom "spherical" Si₂O₆B₃ cores. The dimensions of the Si₂O₆B₃ cores in compounds 2, 3, 4, 6 and 9 are remarkably similar. The reaction between [Bu^tSi{O(PhB)O}₃SiBu^t] (1), and excess pyridine yields the 1:1 adduct [Bu^tSi{O(PhB)O}SiBu^t]. NC₅H₅ (12) while the reaction between 1 and N,N,N′,N′-tetramethylethylenediamine in equimolar amounts affords a 2:1 borosiloxane:amine adduct [Bu^tSi{O(PhB)O}₃SiBu^t]₂ · Me₂NCH₂CH₂NMe₂ (13). Compounds 12 and 13 were characterised with IR and (¹H, ¹³C and¹¹B) NMR spectroscopies and the structure of the pyridine complex 12 was determined with X-ray techniques.

Full text of DOI:10.1016/j.poly.2006.12.045

Polyhedron 26 (2007) 2482–2492
www.elsevier.com/locate/poly
Synthetic and X-ray diffraction studies of borosiloxane
cages [R0Si(ORBO)3SiR0] and the adducts of
[ButSi{O(PhB)O}3SiBut] with pyridine or
N,N,N0,N0-tetramethylethylenediamine
a,
b
b
George Ferguson *, Simon E. Lawrence , Lorraine A. Neville ,
b
b,
*
Brian J. O’Leary , Trevor R. Spalding
a
School of Chemistry, The University of St. Andrews, Fife KY16 9ST, UK
Department of Chemistry, University College Cork, National University of Ireland, Cork, Ireland
b
Received 8 November 2006
Available online 20 January 2007
Abstract
Eleven borosiloxane [R0Si(ORBO)3SiR0] compounds where R0 = But and R = Ph (1), 4-PhC6H4 (2), 4-ButC6H4 (3), 3-NO2C6H4 (4),
4-CH(O)C6H4 (5), CpFeC5H4 (6), 4-C(O)CH3C6H4 (7), 4-ClC6H4 (8), 2,4-F2C6H3 (9), and R0 = cyclo-C6H11 and R = Ph (10), and 4-
BrC6H4 (11) have been synthesized and characterized by spectroscopic (IR, NMR), mass spectrometric and, for compounds where
R0 = But and R = 4-PhC6H4 (2), 4-ButC6H4 (3), 3-NO2C6H4 (4), CpFeC5H4 (6) and 2,4-F2C6H3 (9), X-ray diffraction studies. These
compounds contain trigonal planar RBO2 and tetrahedral R0SiO3 units located around 11-atom ‘‘spherical’’ Si2O6B3 cores. The dimen-
sions of the Si2O6B3 cores in compounds 2, 3, 4, 6 and 9 are remarkably similar. The reaction between [ButSi{O(PhB)O}3SiBut] (1), and
excess pyridine yields the 1:1 adduct [ButSi{O(PhB)O}SiBut]. NC5H5 (12) while the reaction between 1 and N,N,N0,N0-tetramethylethy-
lenediamine in equimolar amounts affords a 2:1 borosiloxane:amine adduct [ButSi{O(PhB)O}3SiBut]2 Æ Me2NCH2CH2NMe2 (13). Com-
pounds 12 and 13 were characterised with IR and (1H, 13C and11B) NMR spectroscopies and the structure of the pyridine complex 12
was determined with X-ray techniques.
Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: Borosilicate; Borosiloxanes; Cage compounds; X-ray diffraction; Structures
1. Introduction
species are relatively rare [3] but previously reported boro-
siloxane cage compounds that have been structurally char-
acterised include [ButSi{O(4-BrC6H4B)O}3SiBut] which
contains the 11-atom ‘‘spherical’’ B3Si2O6 core [4],
[B(OSiPh2SiPh2O)3B] with a ‘‘cylindrical’’ B2Si6O6 core
[5], ‘‘cube-based’’ [(ButSi)4(4-RC6H4B)4O10] species where
R = (CH2@CH) [6] or Br [7] which have B4Si4O10 cores,
and silesesquioxane-based species which contain ‘‘cube-
based’’ BSi7O12 units [8]. One overall intention of the work
carried out by our group [3–7] was to synthesise a variety of
three-dimensional structures which could be reacted fur-
ther to produce new molecular scaffolds in a controlled
way. We now report the extension of the chemistry of the
The chemistry of three-dimensional cage species con-
taining only main group elements bonded by two center–
two electron bonds is notable for the large number of
silesesquioxanes [(RSi)8O12] which have been reported [1].
For cages containing main group 13 elements, aluminium
systems are perhaps the most studied with aluminium–
nitrogen compounds predominant [2]. Boron containing
*
Corresponding authors.
E-mail addresses: gf3@st-andrews.ac.uk (G. Ferguson), t.spalding@
ucc.ie (T.R. Spalding).
0277-5387/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.12.045

G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
2483
Initial characterisation of 1–11 by chemical analysis was
followed by spectroscopic (FT-IR, NMR) and, in some
cases, mass spectrometric analysis. For the compounds
with R0 = But and R = 4-PhC6H4 (2), 4-ButC6H4 (3),
3-NO2C6H4 (4), CpFeC5H4 (6), and 2,4-F2C6H3 (9), sin-
gle-crystal X-ray diffraction studies were carried out. A
summary of crystal data for these compounds is given in
Section 4.
2.2. Crystal and molecular structures of [ButSi-
{O(4-PhC6H4B)O}3SiBut] (2), [ButSi{O(4-ButC6H4B)-
O}3SiBut] (3), [ButSi{O(3-NO2C6H4B)O}3SiBut] (4),
[ButSi{O(CpFeC5H4B)O}3SiBut] (6), and [ButSi-
{O(2,4-F2C6H3B)O}3SiBut] (9)
Comparison of the structures of compounds [ButSi(O-
BRO)3SiBut] where R = 4-PhC6H4 (2), 4-ButC6H4 (3),
3-NO2C6H4 (4), CpFeC5H4 (6) and 2,4-F2C6H3 (9) reveals
that the structural details of the Si2O6B3 cages are remark-
ably similar, Table 1.
Diagram 1.
‘‘spherical’’ cage borosiloxanes with the syntheses of 11
analogues of [R0Si(OBRO)3SiR0] with a wide variety of R
groups, Diagram 1.
The details of the structures of five of these compounds
have been determined with X-ray crystallography. Addi-
tionally, we have studied the reactions between
[ButSi{O(PhB)O}3SiBut] (1) and (a) pyridine or (b)
N,N,N0,N0-tetramethyl-ethylenediamine and established
the solid-state structure of the adduct [ButSi{O(PhB)O}Si-
But] Æ NC5H5 (12).
All five compounds contain two tetrahedral ButSiO3-
units and three trigonal planar RBO2-units held together
by an 11-atom Si(OBO)3Si framework. Figs. 1–3 show
ORTEP views of molecules with R = 4-PhC6H4 (2),
4-ButC6H4 (3) and CpFeC5H4 (6) from
a general
perspective.
The structures of compounds 2 and 6 are shown viewed
along the axes passing through both silicon atoms in Figs.
4 and 5, respectively. The tert-butyl groups attached to the
silicon atoms in compounds 2 and 6 are in ‘‘eclipsed’’
arrangements. The same structural motif is found in 3, 4,
6 and 9.
2. Results and discussion
2.1. Syntheses and structural studies of
[R0Si(ORBO)3SiR0] borosiloxanes 1 to 11
The C6-rings attached to the boron atoms in 2 and 3 are
arranged in a ‘‘paddlewheel’’ formation, see Fig. 4, and are
almost co-planar with the adjacent Si–O–B–O–Si bonded
sequence. The same structural motif was observed in 3, 4,
and 9, and in the compound [ButSi{O(4-BrC6H4B)O}3Si-
But] [4]. A similar situation is observed in the ferrocenyl
compound [ButSi{O(CpFeC5H4B)O}3SiBut] (6), where
the C5H4 ring is almost co-planar with the attached boro-
siloxane group, Fig. 5. The reason for the preference for
co-planarity may reside in a partial overlap of the p system
of the aromatic C6-ring and some delocalised bonding in
the Si–O–B–O–Si sequence. However, it is also possible
that the co-planarity is due to ‘‘crystal packing’’ forces. It
is interesting to note that in the case of 6 the ferrocenyl
groups are not all arranged to give a pseudo-D3h molecular
symmetry. The reasons are unclear but may be due either
to weak intramolecular Hꢀ ꢀ ꢀp–C5H5 ring interactions or
more general ‘‘crystal packing’’ forces.
All the borosiloxane cages with the formulae [R0Si-
(ORBO)3SiR0] were synthesised in a Dean-Stark apparatus
by water elimination reactions between R0Si(OH)3
(R0 = But or cyclo-C6H11) and boronic acids RB(OH)2 in a
2:3 molar ratio in toluene solution heated at the reflux tem-
perature, Eq. (1). In general the tert-butyl compounds were
isolated in 30–40% higher yields than the corresponding
cyclohexyl derivatives with the same R groups.
2R0Si(OH)3 + 3RB(OH)2 ! [R0Si(ORBO)3SiR0]
ð1Þ
where R0 = But and R = Ph (1), 4-PhC6H4 (2), 4-ButC6H4
(3), 3-NO2C6H4 (4), 4-CH(O)C6H4 (5), CpFeC5H4 (6),
4-C(O)CH3C6H4 (7), 4-ClC6H4 (8), 2,4-F2C6H3 (9), and
R0 = cyclo-C6H11 and R = C6H5 (10), and 4-BrC6H4 (11).
An alternative route via the reactions between
tert-butyltrichlorosilane or cyclohexyltrichlorosilane and
boronic acids in the presence of an amine, either Et3N
or aniline, afforded the products 1 to 9 in 5–10% lower
yields and compounds 10 and 11 in ca. 30% lower
yields. Attempts to use phenyl- or tolyltrichlorosilane
reagents afforded boroxines as the only characterisable
products.
The B–O lengths in 2, 3, 4, 6 and 9 range from 1.348(5)
to 1.380(4) and are at the upper end of the reported range
for trigonal boron species with Si–O–B bonds i.e. 1.313(2)
t
˚
in ðOBFÞðOSiBu2Þ2ðOSiMe2Þ (13) [9] to 1.374(7) A in
[B(OSiPh2SiPh2O)3B] (14) [5]. They are similar to B–O
distances in the previously reported spherical cage
[ButSi{O-(4-BrC6H4B)O}3SiBut] (15) [4], which were

2484
G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
Table 1
t
t
t
˚
Selected bond distance (A) and angle (°) data for [Bu Si(OBRO)3SiBu ] where R = 4-PhC6H4 (2), 4-Bu C6H4 (3), 3-NO2C6H4 (4), CpFeC5H4 (6) and 2,4-
F2C6H3 (9)
Compound
2
3
4
6
9
Range of Si–O distances
Mean Si–O
Range of B–O distances
Mean B–O
Mean B–C
Mean Si–C
1.615(2)–1.6212(19)
1.620(2)
1.353(4)–1.380(4)
1.365(4)
1.553(4)
1.833(3)
1.613(3)–1.624(3)
1.620(3)
1.348(5)–1.376(6)
1.364(6)
1.546(6)
1.841(5)
1.603(3)–1.631(3)
1.620(3)
1.354(5)–1.370(5)
1.364(5)
1.559(6)
1.829(4)
1.621(3)–1.637(2)
1.628(3)
1.359(4)–1.373(5)
1.369(5)
1.541(5)
1.851(4)
1.620(4)
1.620(4)
1.372(6)
1.372(6)
1.544(12)
1.838(11)
Range of B–O–Si angles
Mean B–O–Si
Range of O–Si–O angles
Mean O–Si–O
Range of O–B–O angles
Mean O–B–O
Range of O–B–C angles
Mean O–B–C
135.3(2)–142.9(2)
138.6(2)
107.53(11)–110.51(11)
109.18(11)
120.9(3)–121.5(3)
121.1(3)
118.0(3)–120.4(3)
119.4(3)
135.0(3)–143.0(3)
138.7(3)
107.90(17)–110.05(17)
109.19(17)
120.6(4)–121.4(4)
121.0(4)
118.8(4)–120.2(4)
119.5(4)
134.0(3)–143.0(3)
138.5(3)
108.12(14)–110.32(15)
109.03(15)
121.0(4)–122.2(4)
121.8(4)
117.7(4)–120.1(4)
119.0(4)
133.9(2)–142.4(2)
137.8(2)
107.31(13)–110.90(13)
109.08(13)
120.7(3)–121.1(3)
120.9(6)
118.8(3)–120.1(3)
119.5 (3)
139.4(5)
139.4(5)
109.14(15)
109.14(15)
120.6(8)
120.6(8)
119.7.(4)
119.7.(4)
Fig. 1. An ORTEP view of [ButSi{O(4-PhC6H4B)O}3SiBut] (2) with atom numbering.
Fig. 2. An ORTEP view of [ButSi{O(4-ButC6H4B)O}3SiBut] (3), with atom numbering.

G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
2485
Fig. 3. An ORTEP view of [ButSi{O(CpFeC5H4B)O}3SiBut] (6), with atom numbering.
Fig. 4. ORTEP view of [ButSi{O(4-PhC6H4B)O}3SiBut] (2) along the Siꢀ ꢀ ꢀSi axis.
˚
1.364(11)–1.372(10) A and in the cube-based structure
The Si–O distances in 2, 3, 4, 6 and 9 vary between
t
˚
˚
[(Bu Si)4(CH2@CHC6H4B)4O10] [6] (1.361(4)–1.369(4) A).
A mean value of 1.367 A has been reported for B–O dis-
1.603(3) and 1.638(3) A, but the mean values of the six
˚
˚
Si–O distances are remarkably similar at about 1.620 A,
tances where the boron is tricoordinated [10] and the mean
values of the B–O distances reported here are all the same
within one s.u.
Table 1. The range of previously reported Si–O distances
for borosiloxanes containing trigonal boron was 1.603(2)
[7] to 1.655(5) [4,11]. The mean values of Si–O distances

2486
G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
Fig. 5. ORTEP view of [ButSi{O(CpFeC5H4B)O}3SiBut] (6) along the Siꢀ ꢀ ꢀSi axis.
in [B(OSiPh2SiPh2O)3B] (14) [5], [ButSi{O(4-BrC6H4B)O}3-
SiBut] (15) [4] and [(ButSi)4(CH2@CHC6H4B)4O10] [6],
these angles vary from 134.0(3)° to 143.0(3)° with a mean
value of 138.5(3)°. The B–O–Si angles in 6 range from
133.9(3)° to 142.4(3)° with a mean value of 137.8(9)°. Com-
pound 9 has a symmetry determined single B–O–Si angle of
139.5(4)°. All B–O–Si angles for 2, 3, 4, 6 and 9 are notably
similar to those for [B(OSiPh2SiPh2O)3B] (14) [5], and [But-
Si{O(4-BrC6H4B)O}3SiBut] (15) [4] where the B–O–Si
angles varied over the range 137.89(18)–140.03(18)° with
a mean value of 138.6(18)° for 14 and 137.5(6)–140.7(6)°
with a mean value of 138.6(6)° for 15, respectively. In the
more open structure of the cube-based [(But-
Si)4(CH2@CHC6H4B)4O10] [6], the B–O–Si angles vary
more from 137.5(2)° to 154.4(2)°.
Like the B–O–Si angles, the O–B–O angles in 2, 3, 4, 6
and 9 are notably similar and close to 121°, Table 1. The
three O–B–O angles in [ButSi{O(4-BrC6H4B)O}3SiBut]
(15) [4] varied from 119.9(8)° to 124.0(8)° the mean value
being 122.2(8)° and the four O–B–O angles in [(But-
Si)4(CH2@CHC6H4B)4O10] [6], varied from 120.7(3)° to
120.9(3)° with a mean value of 120.8(3)°.
The O–Si–O and O–B–C angles in 2, 3, 4, 6 and 9 are
even more remarkably similar with ranges and means
which are almost identical, Table 1. The range over all
the compounds for O–Si–O angles is from 107.29(15)° to
110.90(15)° both of which were observed in [ButSi{O(Cp-
FeC5H4B)O}3SiBut] (6). The mean value of O–Si–O angles
in 2, 3, 4, 6 and 9 was 109.12° which was very close to the
mean value observed in [(ButSi)4(CH2@CHC6H4B)4O10]
[6]. For [B(OSiPh2SiPh2O)3B] (14) [5], the three O–Si–O
angles ranged from 108.78(12)° to 109.34(10)° with a mean
˚
were 1.631(2), 1.621(5) and 1.616(4) A, respectively, and a
˚
mean value of 1.631(2) A has been reported for Si–O dis-
tances where the silicon is four coordinated [10].
The mean B–C distances in 2, 3, 4, 6 and 9 range from
˚
1.541(5) to 1.559(6) A. The B–CPh distances in PhB(O-
SiPh3)2, 16 [12] and (PhBO)2(OSiPh2)2 (17) [13], were
˚
1.558(8) and 1.555(6) A, respectively, and the B–C dis-
tances reported in [ButSi{O(4-BrC6H4B)O}3SiBut] (15) [4]
˚
ranged from 1.541(11) to 1.585(11) A, with a mean value
˚
of 1.566 A.
The average value of the Si–C distances in 2, 3, 4, 6 and
˚
9 were 1.833(3), 1.841(5), 1.829(4), 1.853(4) and 1.846(9) A,
˚
respectively. A mean value of 1.863 A has been reported
for Si–C bonds, where C is sp3-hybridised and bonded to
carbon or hydrogen atoms only and the silicon atom is four
coordinated [10].
B–O–Si angles at trigonal boron atoms are known to be
very flexible [12] in both acyclic and cyclic compounds.
Examples include the two chemically equivalent B–O–Si
angles in PhB(OSiPh3)2 (18), {139.8(4)° and 157.9(3)°}
[12], and in cyclic systems, 128.89(14)° in (PhBO)(Ph2SiO)2
(19) [14] and 160.9(3)° in (PhBO)2(Ph2SiO)2 (17) [13].
Hence, it is noteworthy that in the compounds 2, 3, 4
and 6 the variation is relatively small at ca. 4° from a
mean angle of ca. 138°, Table 1. The six B–O–Si angles
in 2 vary from 135.3(2)° to 142.9(2)° with a mean value
of 138.6(2)° and those in 3 show an almost identical range
of 135.0(3)–143.0(3)° and a mean value of 138.8(3)°. In 4

G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
2487
value of 109.12(12)°. In [ButSi{O(4-BrC6H4B)O}3SiBut]
(15) [4] the O–Si–O angles ranged from 108.5(3)° to
109.7(3)° with a mean value of 109.2(3)°. The O–B–C
angles range from 118.0(3)° to 120.4(3)° which are both
found in 2. The mean values in compounds 2, 3, 6 and 9
are all close to 119.5° and that in 4 is 119.1°. The O–B–C
angles in compound 15 range from 116.6(9)° to 120.7(8)°
with a mean of 118.9(8)°.
with the removal of any B–O p-bonding component
on going from trigonal to tetrahedral coordination at
boron.
The Si–O distances in 2, 3, 4, 6 and 9 varied between
˚
˚
1.603(3) and 1.638(3) A, with a mean value of 1.621 A
and these values are comparable with the four Si–O dis-
tances in [ButSi{O(PhB)O}3SiBut] Æ NC5H5 (12) which
˚
range from 1.625(9) to 1.631(9) A where the boron atom
is tricoordinate. The average value is 1.628 A. The two
˚
As with the O–Si–O angles, the O–Si–C angles are close
to the tetrahedral value in all cases.
Si–O distances where the boron atom is tetracoordinate
are notably shorter with values of 1.585(7) and
˚
2.3. Reactions between the borosiloxane cage
[ButSi(OPhBO)3SiBut] and pyridine or N,N,N0,N0-
tetramethylethylenediamine
1.594(9) A suggesting that electron density has increased
in the Si–O bond corresponding to the decrease in B–O
electron density.
The B–N distance in [ButSi{O(PhB)O}3SiBut] Æ NC5H5
˚
2.3.1. Synthesis and structural study of
[ButSi(OPhBO)3SiBut] Æ NC5H5 (12)
(12) was 1.655(17) A. For simple borosiloxane Ph(OSi-
R2R0)B{O(CH2)3N} species, 20, the B–N distances are
The reaction between [ButSi{O(PhB)O}3SiBut] (1), and
three equivalents of pyridine in ether at r.t. for 16 h
followed by crystallisation of the solid product from
dichloromethane–heptane (1:3) afforded [ButSi{O(Ph-
B)O}3SiBut] Æ NC5H5 (12) in 73% yield. This compound
was soluble in toluene, dichloromethane, ether and ace-
tone at room temperature. Chemical analysis for C, H,
B and N supported the formulation of 12 as a 1:1 adduct.
The 11B NMR spectrum of 12 showed two signals in a 2:1
ratio with one corresponding to three coordinate boron at
25.4 ppm and one associated with four coordinate boron
at 0.6 ppm, respectively. Crystals of [ButSi{O(PhB)O}3Si-
But] Æ NC5H5 (12) suitable for X-ray diffraction studies
were grown by the slow evaporation of a dichlorometh-
ane–heptane solution of 12. Fig. 6 is an ORTEP plot
1.639(4) [15] and 1.639(6) A [16] in the Ph2Me and PhMe2
˚
˚
derivatives, respectively. A value of 1.556 A has been
reported for B–N distances where the boron atom is tetra-
coordinate [10].
The two B–C distances in 12 with the boron atom trico-
˚
˚
ordinate were 1.552(19) A and 1.594(19) A. Similar B–C
distances in 2, 3, 4, 6 and 9 with mean values of 1.553(4),
˚
1.546(6), 1.559(6), 1.541(5) and 1.544(10) A were noted in
˚
Table 1. A mean value of 1.556 A has been reported for
B–Car distances, where the boron atom is tricoordinate
and the carbon atom is part of an aromatic system [10].
The B–C distance in 12 where the boron atom is tetracoor-
˚
dinate was 1.58(2) A which is within 3x s.u. of the two
other B–C distances. The mean Si–C distance in 12 was
˚
typical of such distances at 1.832(15) A.
showing
a
general view of [ButSi{O(PhB)O}3SiBu-
In [ButSi{O(PhB)O}3SiBut] Æ NC5H5 (12) the four B–O–
Si angles in which the boron is tricoordinate range from
134.4(10)° to 140.7(9)° which is a similar range to the cor-
responding angles in 2, 3, 6 and 9, Table 1. The two B–O–Si
angles in 12 where the boron is tetracoordinate are
134.2(8)° and 138.0(9)°.
t] Æ NC5H5 (12), and the atom numbering scheme is shown
in Fig. 6. Significant bond distance and bond angle data
for 12 are given in Table 2. The basic Si2O6B3 cage struc-
ture of [ButSi{O(PhB)O}3SiBut] Æ NC5H5 (12) is very sim-
ilar to the Si2O6B3 cage in the borosiloxanes 2, 3, 6 and 9
reported above. The structure of 12 also involves near-
eclipsed arrangements of the tert-butyl groups at Si(1)
with those at Si(21) and a ‘‘paddlewheel’’ arrangement
of the three phenyl groups and the pyridine group is
adopted as can be seen if the structure is viewed above
the Si(1)ꢀ ꢀ ꢀSi(21) axis.
The O–B–O angles in [ButSi{O(PhB)O}3SiBut] Æ NC5H5
(12) vary from 111.6(11)° at the tetracoordinate boron
atom to 121.1(13)° and 122.3(13)° at the tricoordinate
boron atoms. These angles are close to the 109° and 120°
expected for tetrahedral and trigonal planar geometries,
respectively. Likewise the O–Si–O angles in 12 range from
108.2(5)° to 111.0(5)° with a mean value of 109.6(5)° which
is normal for tetrahedral silicon and the four O–B–C angles
in [ButSi{O(PhB)O}3SiBut] Æ NC5H5 (12) where the boron
is trigonal planar range from 117.9(12)° to 120.1(13)°.
The two O–B–C values in 12 where the boron atom is tet-
rahedral had values greater than 109° at 112.6(11)° and
115.5(12)°, respectively.
The four B–O distances in [ButSi{O(PhB)O}3SiBut] Æ
NC5H5 (12) for the tricoordinate boron atoms span a rel-
˚
atively wide range from 1.354(17) to 1.394(18) A. The
two B–O distances for the tetracoordinate bonded boron
˚
atom in 12 are 1.457(18) and 1.469(18) A, Table 2. These
values are similar to data from the tetrahedrally coordi-
nated boron compounds Ph(OSiR2R0)B{O(CH2)3N}
(20), where the boron atom is directly bonded to two
oxygen atoms, a Ph group and the nitrogen atom and
R or R0 = Ph or Me. These compounds have B–OSi dis-
tances of 1.439(4) [15] and 1.443(6) [16] in the Ph2Me
and PhMe2 derivatives, respectively. The increased B–O
distance at the tetrahedral boron site may be associated
The six O–Si–C angles in 12 ranged from 106.4(6)° to
112.6(5)° with a mean value of 109.4(6)° but the angles
where the oxygen is bonded to a tetracoordinate boron
atom, mean value 112.4(6)°, appeared to be larger than
the O–Si–C angles where the oxygen is bonded to a trigonal
boron, mean value 107.9(6)°.

2488
G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
Fig. 6. An ORTEP view of [ButSi(OPhBO)3SiBut] Æ NC5H5 (12), with atom numbering. Selected interatomic distances (A) and angles (°): Si(1)–O(11)
1.594(9), Si(1)–O(21) 1.630(9), Si(1)–O(31) 1.631(9), Si(1)–C(1) 1.832(15), Si(2)–O(12) 1.585(7), Si(2)–O(22) 1.626(9), Si(2)–O(32) 1.625(9), Si(2)–C(2)
1.831(14), B(1)–N(11) 1.655(17), B(1)–O(11) 1.457(18), B(1)–O(12) 1.469(18), B(1)–C(111) 1.58(2), B(2)–O(21) 1.394(18), B(2)–O(22) 1.370(17), B(2)–C(21)
1.552(19), B(3)–O(31) 1.354(17), B(3)–O(32) 1.375(19), B(3)–C(31) 1.594(19); O(11)–Si(1)–O(21) 111.0(5), O(11)–Si(1)–O(31) 109.6(5), O(21)–Si(1)–O(31)
108.2(5), O(11)–Si(1)–C(1) 111.8(6), O(21)–Si(1)–C(1) 106.4(6), O(31)–Si(1)–C(1) 109.7(6), O(12)–Si(2)–O(22) 109.3(5), O(12)–Si(2)–O(32) 110.6(5), O(22)–
Si(2)–O(32) 108.6(5), O(12)–Si(2)–C(2) 112.6(5), O(22)–Si(2)–C(2) 106.4(6), O(32)–Si(2)–C(2) 109.2(6), B(1)–O(11)–Si(1) 138.0(9), B(2)–O(21)–Si(1)
139.7(9), B(3)–O(31)–Si(1) 134.4(10), B(1)–O(12)–Si(2) 134.2(8), B(2)–O(21)–Si(2) 137.3(9), B(3)–O(32)–Si(2) 140.7(9), O(12)–B(1)–O(11) 111.6(11),
O(11)–B(1)–C(111) 115.5(12), O(12)–B(1)–C(111) 112.6(11), O(11)–B(1)–N(11) 103.2(10), O(12)–B(1)–N(11) 104.9(11), C(111)–B(1)–N(11) 107.9(10),
O(21)–B(2)–C(21) 120.1(13), O(21)–B(2)–C(22) 118.8(12), O(21)–B(2)–O(22) 121.1(13), O(31)–B(3)–O(32) 122.3(13), O(32)–B(3)–C(31) 117.9(12), O(31)–
B(3)–C(31) 119.8(13).
˚
Table 2
Summary of crystal data details for 2, 3, 4, 6, 9 and 12
Crystal data
2
3
4
6
9
12
Empirical formula
Molar mass
Color
C
44H45B3O6Si2
C38H57B3O6Si2
698.45
colourless
needle
12.5922(16)
13.8371(18)
24.674(2)
90.00
93.830(9)
90.00
C29.5H33.5B3N3O12Si2
710.70
colourless
block
9.533(2)
20.295(3)
18.697(3)
90.00
101.775(12)
90.00
C38H45B3Fe3O6Si2
853.9
orange
C26H27B3F6O6Si2
638.09
colourless
cube
15.6121(8)
15.6121(8)
15.6121(8)
90.00
90.00
90.00
3805.3(3)
P4132
C31H38B3NO6Si2
609.23
colourless
block
11.030(6)
18.227(6)
16.235(5)
90.00
94.24(3)
90.00
3255(2)
Cc
758.41
colourless
plate
12.9156(17)
15.6120(9)
22.678(2)
90.00
103.899(9)
90.00
4311.0(7)
P21/c
Habit
block
˚
a (A)
10.4736(11)
10.9281(14)
19.0690(28)
97.905(11)
102.628(10)
106.750(10)
1991.9(4)
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
4289.6(10)
P21/c
4
3541.4(11)
P21/c
4
ꢀ
Space group
Z
P1
4
2
4
4
F(000)
1600
1.169
0.127
294(1)
8019
0.0549
0.1085
0.916
1504
1.081
0.122
294(1)
7964
0.0638
0.1709
1.043
1482
1.333
0.164
293(2)
3338
0.0739
0.1497
0.919
884
1312
1.114
0.153
293(2)
1288
1.243
0.152
150(2)
2828
0.0711
0.1569
1.104
Dcalc (g cmꢁ1
)
1.424
1.182
293(2)
9117
0.0427
0.0987
1.151
l (mmꢁ1
T (K)
Reflections measured
R
Rw
)
657
0.0828
0.1391
1.197
Goodness-of-fit

G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
2489
Diagram 2.
2.4. Synthesis of [ButSi{O(PhB)O}3SiBut]2 Æ
Me2NCH2CH2NMe2 (13)
involve near eclipsed arrangements of the tert-butyl
groups at Si(1) and Si(2) when viewed along the Siꢀ ꢀ ꢀSi
axis. The B–O–Si angles in the B3Si2O6 cores of 2, 3, 4,
6 and 9 are found in a relatively narrow range from
134.0° to 143.0°. The structure of the pyridine adduct,
12, was determined with X-ray techniques. It had two tri-
gonal planar RBO2 units and one tetrahedral RBO2N
unit and a number of features in common with the un-
adducted compounds including a narrow range of B–O–
Si angles (133.2–140.9°).
The reaction between [ButSi{O(PhB)O}3SiBut] (1), and
one equivalent of N,N,N0,N0-tetramethylethylenediamine
in ether at r.t. for 8 h afforded [ButSi{O(PhB)O}3SiBut]2 Æ
Me2NCH2CH2NMe2 (13) in low yield (27%) after crystalli-
sation of the crude product from CH2Cl2–heptane (1:2) solu-
tion. As with compounds 1–12, this compoundwas soluble in
typical organic solvents such as toluene, dichloromethane,
ether and acetone at room temperature. Chemical analysis
for C, H, B and N suggested the formulation of 13 as a 2:1
adduct and FT-IR and multinuclear NMR spectroscopy
supported this formulation. The 11B NMR spectrum showed
signals at 31.8 and 2.8 ppm in a ratio of 2:1 which correspond
to three and four coordinate boron environments, respec-
tively. On the basis of these data we suggest that the overall
structure of 13 is as shown in Diagram 2.
4. Experimental
All reactions were carried out under an inert atmosphere
of dry nitrogen. Solvents were dried and distilled prior to
use. Both tert-butylsilanetriol and cyclo-hexylsilanetriol
were prepared according to the literature synthesis of But-
Si(OH)3 [17]. All boronic acids used were obtained from
either Aldrich or Lancaster Chemical Co. and used as sup-
plied. Infrared spectra were recorded as KBr disks on a
Unfortunately, crystals suitable for an X-ray diffraction
study could not be obtained even after many attempts from
many different solvents.
1
Perkin–Elmer Paragon 1000 FT-IR Spectrometer. H and
13C NMR spectra were recorded in CDCl3 solvent on a
JEOL FT NMR Spectrometer, GSX-270 Series or, for
11B and 29Si NMR spectra, on a Bruker AM 400. Chemical
shifts d are expressed in ppm relative to N = 100 MHz for d
(1H) (quoted 0.05 ppm) (standard SiMe4) and N = 32.083
3. Conclusions
Eleven borosiloxane [R0Si(ORBO)3SiR0] cage com-
pounds (R0 = But and R = Ph (1), 4-PhC6H4 (2), 4-ButC6H4
(3), 3-NO2C6H4 (4), 4-CH(O)C6H4 (5), CpFeC5H4 (6), 4-
C(O)CH3C6H4 (7), 4-ClC6H4 (8) and R = 2,4-F2C6H3 (9),
and R0 = cyclo-C6H11 and R = Ph (10) and 4-BrC6H4
(11)) have been synthesized and characterized by spectro-
scopic (IR, NMR), mass spectrometric and for compounds
where R0 = But and R = 4-PhC6H4 (2), 4-ButC6H4 (3), 3-
NO2C6H4 (4), CpFeC5H4 (6) and 2,4-F2C6H3 (9) X-ray dif-
fraction studies. These compounds contain trigonal planar
RBO2 and tetrahedral R0SiO3 units located around 11-atom
‘‘spherical’’ B3Si2O6 cores. The reaction between [But-
Si{O(PhB)O}3SiBut], 1, and excess pyridine yields a 1:1
adduct while the reaction between 1 and N,N,N0,N0-tetra-
methylethylenediamine in equimolar amounts affords a 2:1
borosiloxane:amine adduct.
971 MHz for d (11B) (quoted
0.5 ppm) (nominally
F3BOEt2 in CDCl3). Mass spectra (EI, 70 eV) were
recorded on a Kratos Profile GC–MS Spectrometer. Ele-
mental analyses were carried out on a Perkin–Elmer
240C elemental analyser at the Microanalytical Labora-
tory, University College, Cork.
4.1. Syntheses of borosiloxane [R1Si(ORBO)3SiR1] cage
compounds (R1 = But and R = Ph (1); 4-PhC6H4 (2);
4-ButC6H4 (3); 3-NO2C6H4 (4); 4-CH(O)C6H4 (5);
CpFeC5H4 (6); 4-C(O)CH3C6H4 (7); 4-ClC6H4 (8);
2,4-F2C6H3 (9); and R1 = cyclo-C6H11 and R = Ph (10);
4-BrC6H4 (11))
It is clear from the structural analyses of 2, 3, 4, 6 and
9 that the B3Si2O6 core structures are very similar and
those in 2 and 3 being almost identical. All the structures
4.1.1. Synthesis of [ButSi{O(PhB)O}3SiBut] (1)
A mixture of tert-butylsilanetriol (0.507 g, 3.72 mmol)
and phenylboronic acid (0.680 g, 5.58 mmol) in toluene

2490
G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
(50 ml) was heated at reflux temperature in a Dean-Stark
apparatus for 10 h. After cooling, the removal of toluene
on a rotary evaporator (40 °C) yielded a colourless solid.
This was crystallised from hot benzene (50°C) affording
[ButSi{O(PhB)O}3SiBut] (153, 0.943 g, 95.7%), m.p. 220–
222°C. Anal. Calc. for C26H33B3O6Si2: C, 58.9; H, 6.3; B,
[M]+, 619 [MꢁNO2]+, 608 [MꢁBu]+, 451 [Mꢁ2NO2ꢁ
C6H4NO2]+, 122 [C6H4NO2]+, 57 [Bu]+.
4.1.5. Synthesis of [ButSi{O(4-CHOC6H4)BO}3SiBut] (5)
The procedure was the same as that described for 1. The
following quantities were used: tert-butylsilanetriol
(0.4021 g, 2.96 mmol); 4-formylphenylboronic acid
(0.6621 g, 4.41 mmol); toluene, 50 ml; reaction time 18 h.
This afforded [ButSi{O(4-CHOC6H4)BO}3SiBut] (5) as a
colourless crystalline solid (0.75 g, 82.1%), mp 194–
196 °C. Anal. Calc. for C29H33O9B3Si2: C, 56.7; H, 5.4.
6.1. Found: C, 59.05; H, 6.2; B, 6.0%. FT-IR (KBr) mmax
/
cmꢁ1: 1305(vs), 1133(vs), 677(s). 1H NMR (CDCl3,
294 K): d: 7.91–7.22 [m, 5H, C6H5]; 1.35 [s, 6H,
C(CH3)3]. 13C NMR (CDCl3, 294 K) d: 135.5, 133.4,
132.2, 127.9 [all C6H5]; 25.5 [C(CH3)3]; 16.6 [C(CH3)3].
MS, m/z: 530 [M]+, 473 [MꢁBu]+, 453 [MꢁPh]+.
Found: C, 56.5; H, 5.6%. FT-IR (KBr) mmax/cmꢁ1
:
1298(vs), 1128(vs), 681(s). 1H NMR (CDCl3, 294 K): d
9.98 [s, 3H, C6H4CHO], 8.00–7.19 [m, 4H, C6H4CHO],
1.27 [s, 6H, C(CH3)3], 13C NMR (CDCl3, 294 K): d 192.4
[C6H4CHO], 138.7, 135.8, 128.9 [all C6H4CHO],
25.8C(CH3)3], 16.2 [C(CH3)3]. MS, m/z: 614 [M]+, 105
[C6H4CHO]+, 57 [Bu]+.
4.1.2. Synthesis of [ButSi{O(4-C6H5C6H4)BO}3SiBut (2)
The procedure was the same as that described for 1. The
quantities used were: tert-butylsilanetriol (0.1536g,
1.13 mmol); 4-biphenylboronic acid (0.3254g, 1.64 mmol);
toluene 50ml; reaction time 18 h. Crystallisation from
CH2Cl2–heptane (1:3) afforded [ButSi{O(4-C6H5C6H4)-
BO}3SiBut], 2 (0.35 g, 81.1%), mp 282–284 °C. Anal. Calc.
for C44H45O6B3Si2: C, 69.7; H, 6.3. Found: C, 69.6; H,
6.3%. FT-IR (KBr) mmax/cmꢁ1: 1299(vs), 1132(vs), 660(s).
4.1.6. Synthesis of [ButSi{O(CpFeC5H4)BO}3SiBut] (6)
The procedure was the same as that described for 1. The
following quantities were used: tert-butylsilanetriol
(0.1971 g, 1.45 mmol); ferrocenylboronic acid (0.5211 g,
2.25 mmol); toluene, 60 ml; reaction time 15 h. Crystallisa-
tion from CH2Cl2–heptane (1:3) afforded orange crystals of
[ButSi(OC5H4FeCpBO)3SiBut] (6) (0.50 g, 82.2%), m.p.
244–246 °C. Anal. Calc. for C38H45O6B3Fe3Si2: C, 53.4;
1H NMR (CDCl3, 294 K):
d
8.03–7.21 [m, 3H,
C6H4C6H5], 1.33 [s, 2H, C(CH3)3], 11B NMR (CDCl3,
294 K) d 28.3, 13C NMR (CDCl3,294 K) d 144.4, 141.0,
135.9, 131.0, 127.9, 126.8, 126.5 [all C6H4C6H5], 26.6
[C(CH3)3], 16.3 [C(CH3)3], 29Si NMR (CDCl3, 294 K) d
ꢁ57.5. Crystal data for 2, see Table 1.
H, 5.3. Found: C, 53.4; H, 5.3%. FT-IR (KBr) mmax
/
cmꢁ1: 1316(s), 1290(s), 621(m). MS, m/z: 854 [M]+, 186
[(C5H5FeC5H5)]+. Crystal data for 6: see Table 1.
4.1.3. Synthesis of [ButSi{O(4-ButC6H4)BO}3SiBut] (3)
The procedure was the same as that described for 1. The
quantities used were: tert-butylsilanetriol (0.1311 g,
0.96 mmol); tert-butylphenylboronic acid (0.2548 g,
1.43 mmol); toluene 50 ml; reaction time 15 h. Crystallisa-
tion from CH2Cl2–heptane (1:2) afforded [ButSi{O-
(4ButC6H4)BO}3SiBut] (3) (0.24 g, 74.9%). mp 253–255 °C.
Found: C, 65.3; H, 8.2. Anal. Calc. for C38H57O6B3Si2:
C, 65.3; H, 8.2. Found: C, 65.3; H, 8.2. FT-IR (KBr)
4.1.7. Synthesis of [ButSi{O(CH3C(O)C6H4B)O}3SiBut]
(7)
The procedure was the same as that described for 1. The
following quantities were used: tert-butylsilanetriol
(0.3024 g,
2.22 mmol);
4-acetylphenylboronic
acid
(0.5511 g, 3.31 mmol); toluene, 50 ml; reaction time 18 h.
This afforded [ButSi{O(CH3C(O)C6H4B)O}3SiBut] (7) as
a crystalline solid (0.54 g, 75.2%), m.p. 134–135 °C. Anal.
Calc. for C32H39O9B3Si2: C, 58.5; H, 6.0. Found: C, 58.6;
H, 6.1%. FT-IR (KBr) mmax/cmꢁ1: 1301(vs), 1133(s),
632(m). 1H NMR (CDCl3, 294 K): d 8.04–7.26 [m, 4H,
C6H4]; 2.62 [s, 3H, C(O)CH3]; 1.27 [s, 6H, C(CH3)3]. 13C
NMR (CDCl3, 294 K): d 198.1 [C(O)CH3]; 139.8, 137.2,
135.9, 134.1, 127.9 [all C6H4]; 27.0 [C(O)CH3]; 25.5
[C(CH3)3], 16.3 [C(CH3)3]. MS, m/z: 656 [M]+, 599
[MꢁBu]+, 57 [Bu]+.
4.1.8. Synthesis of [ButSi{O(4-ClC6H4)BO}3SiBut] (8)
The procedure was the same as that described for 1. The
quantities of starting materials used were: tert-butylsilanet-
riol (0.1541 g, 1.13 mmol); 4-chlorophenylboronic acid
(0.2641 g, 1.67 mmol); toluene 60 ml; reaction time 16 h.
Crystallisation from a toluene–heptane (ca. 1:3) solution
afforded [ButSi{O(4-ClC6H4)BO}3SiBut] (8) (0.29 g,
34.1%), m.p. 304–308 °C. Anal. Calc. for C26H30O6-
B3Cl3Si2: C, 49.4; H, 4.7. Found: C, 49.6; H, 4.5%.
m
max/cmꢁ1: 1302(vs), 1137(s), 660(m). MS, m/z: 698 [M]+,
641 [MꢁBu]+, 57 [Bu]+. Crystal data for 3: see Table 1.
4.1.4. Synthesis of [ButSi{O(3-NO2C6H4)BO}3SiBut] (4)
The procedure was the same as that described for 1.
The quantities used were: tert-butylsilanetriol (0.430 g,
3.16 mmol), 3-nitrophenylboronic acid (0.789 g, 4.73
mmol), toluene, 50ml; reaction time 10 h. The product,
[ButSi{OB(3-C6H4NO2)O}3SiBut] Æ (0.5C7H8), crystallised
from a toluene solution at room temperature. Yield
0.913 g (87.1%) of 4, m.p. 176–178°C. Found: C, 49.9; H,
4.9; N, 5.8; B, 4.3%. Anal. Calc. for C29.5H34B3N3O12Si2:
C, 49.8; H, 4.8; N, 5.9; B, 4.6. Found: C, 49.9; H, 4.9; N,
5.8; B, 4.3%. FT-IR (KBr) mmax/cmꢁ1: 1300(vs), 1143(vs),
1
657(m). H NMR (CDCl3, 294 K): d: 8.67–7.31 [m, 2H,
C6H4NO2]; 1.43 [s, 3H, C(CH3)3]. 13C NMR (CDCl3,
294 K) d: 148.4, 141.4, 134.2, 130.0, 128.7, 127.1 [all
C6H4NO2]; 25.7 [C(CH3)3]; 16.6 [C(CH3)3]. MS, m/z: 665

G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
2491
FT-IR (KBr) mmax/cmꢁ1: 1306(vs), 1130(m), 678(m). 1H
NMR (CDCl3, 294 K): d 7.81–7.20 [m, 2H, C6H4Cl];.
1.26 [s, 3H, C(CH3)3]. (HR-MS), m/z: Found 632.094. Cal-
C, 61.1; H, 6.2; N, 2.3; B, 5.4. Found: C, 61.7; H, 6.3; N,
2.9; B, 5.1%. FT-IR (KBr) mmax/cmꢁ1: 1327(s), 1297(s),
1194(s), 1103(s), 1051(s), 1018(s), 701(s). 1H NMR (CDCl3,
294 K): d 8.80–7.21 [m, 10H, C6H5 and C5H5], 1.32 [s, 9H,
C(CH3)3]. 13C NMR (CDCl3, 294 K): d 147.3, 137.7, 134.3,
130.0, 127.4, 124.3 [all C6H5 and C5H5], 25.6 [C(CH3)3],
16.6 [C(CH3)3]. 11B NMR (CDCl3, 294 K): d 25.5
OB(Ph)O, 0.6 OPhBO(NC5H5). Crystal data for 12: see
Table 2.
12
6
culated for
C
26
1H3011B335Cl3 O628Si2 632.017.
4.1.9. Synthesis of [ButSi{O(2,4-F2C6H3)BO}3SiBut] (9)
The procedure was the same as that described for 1. The
following quantities were used: tert-butylsilanetriol
(0.4112 g, 3.0 mmol); 2,6 difluorophenylboronic acid
(0.6821 g, 4.4 mmol); toluene, 60 ml; reaction time 15 h.
Crystallisation from CH2Cl2–heptane (1:3) afforded [But-
Si{O(2,4-F2C6H3)BO}3SiBut] (9) (0.75 g, 87.3%), m.p.
183–185°C. Anal. Calc. for C36H27B3F6O6Si2: C, 49.0; H,
4.3.2. Synthesis of [ButSi{O(PhB)O}3SiBut]2 Æ
Me2NCH2CH2NMe2 (13)
Compound 1 (0.251 g, 0.473 mmol) was dissolved in
ether (40 ml). N,N,N0,N0-Tetramethylethylenediamine
(0.055 g, 0.472 mmol) was added via micropipette and a
colourless precipitate formed. With further stirring, this
almost completely dissolved. After 8 h, the solution was fil-
tered. Removal of the solvent gave a colourless powder.
Crystallisation from CH2Cl2–heptane (1:2) afforded [But-
Si{O(PhB)O}3SiBut]2 Æ Me2NCH2CH2NMe2 (13) (0.151 g,
27.3%), m.p. 233–234 °C. Anal. Calc. for C58H82O12B6N2-
Si4:C, 59.2; H, 7.0, N, 2.4; B, 5.6. Found: C, 58.8; H, 6.9;
N, 2.2; B, 5.4%. FT-IR (KBr) mmax/cmꢁ1: 1439(s),
1356(s), 1308(vs), 1165(s), 1172(s), 1085(s), 1032(s),
4.3. Found: C, 50.1H, 4.4%. FT-IR (KBr), mmax/cmꢁ1
:
1310(s), 1130(vs), 651(m). 1H NMR (CDCl3, 294 K): d
7.80–6.75[m, 1H, C6H3], 1.26[s, 2H, C(CH3)3]. 29Si NMR
(CDCl3, 294 K) d ꢁ58.12. Crystal data for 9, see Table 2.
4.1.10. Synthesis of [C6H11Si{O(PhB)O}3SiC6H11] (10)
The procedure was essentially the same as that described
for 1. The quantities used were: cyclohexylsilanetriol
(0.4162 g, 2.54 mmol); phenylboronic acid (0.4599 g,
3.77 mmol); toluene 50 ml; reaction time 14 h. Crystallisa-
tion from CH2Cl2, toluene and heptane (1:1:2) afforded
[C6H11Si{O(PhB)O}3SiC6H11] (10) (0.30 g, 42.2%), m.p.
192–194 °C. Anal. Calc. for C30H37O6B3Si2: C, 61.8; H,
1
680(s), 652(s). H NMR (CDCl3, 294 K): d 7.81–7.14 [m,
15H, C6H5]; 2.62 [m, 2H, Me2NCH2CH2NMe2], 2.21 [s,
6H, (CH3)2NCH2-CH2N(CH3)2], 1.34 [s, 18H, C(CH3)3],
13C NMR (CDCl3, 294 K): d 135.5, 134.9, 131.2, 129.7,
6.4. Found: C, 62.1; H, 6.3%. FT-IR (KBr), mmax/cmꢁ1
:
1306(vs), 1140(vs), 639(s). 1H NMR (CDCl3, 294 K): d
7.53–7.17 [m, 15H, C6H5]; 2.12–1.12 [m, 22H, C6H11].
127.4
[all,
C6H5],
55.4
[Me2NCH2CH2NMe2],
44.9[(CH3)2NCH2-CH2N(CH3)2], 26.1 [C(CH3)3], 16.3
[C(CH3)3]. 11B NMR (CDCl3, 294 K): d 31.8 OB(Ph)O
and 2.8 OPhBO(Me2NCH2)2.
4.2. Synthesis of [C6H11Si{O(4-BrC6H4B)O}3SiC6H11]
(11)
The procedure was essentially the same as that described
for 1. The quantities of reagents were: cyclohexylsilanetriol
(0.3199 g, 1.97 mmol), bromophenylboronic acid (0.7011 g,
3.49 mmol); toluene 50 ml; reaction time 10 h. A benzene
solution was layered with cyclohexane (ca. 1:3). The micro-
crystalline product was [C6H11Si{O(4-BrC6H4B)O}3-
SiC6H11] (11) (0.44 g, 57.3%), m.p. 252–254 °C. Anal. Calc.
for C30H34O6B3Br3Si2: C, 44.0; H, 4.2; Br, 29.3. Found: C,
44.0; H, 4.3; Br, 29.4%. FT-IR (KBr), mmax/cmꢁ1: 1300(vs),
4.3.3. Data Collection and structure refinement for
compounds 2, 3, 4, 6, 9 and 12
Data for 2, 3 and 4 were collected on an Enraf-Nonius
CAD-4 diffractometer with graphite-monochromatised
˚
Mo Ka radiation (k = 0.71073 A). Data for 6, 9 and 12
were collected on a Nonius MACH3 diffractometer with
graphite-monochromatised Mo Ka radiation (k =
˚
0.71073 A). Data analysis for 2, 3, 4 [18], 6, 9 and 12 [19]
1
were carried out to provide 8018, 7964, 7780, 9117, 3379
and 5384 independent reflections, respectively. The struc-
tures were solved using direct methods [20]. Non-hydrogen
atoms were refined with anisotropic thermal parameters.
The hydrogen atoms bonded to carbon were included in
geometric positions and given thermal parameters equiva-
lent to 1.2 times those of the atom to which they were
attached, although a 1.5 factor was used for the methyl
groups. A Gaussian absorption correction on 2 was carried
out [18]. For 9 there was disordered solvent present which
could not be modelled correctly and was removed using the
SQUEEZE algorithm [21].
1129(vs), 636(s). H NMR (CDCl3, 294 K): d 7.90–7.25[m,
6H, C6H4Br]; 2.17–2.13 [m, 11H, C6H11].
4.3. Reactions between [ButSi{O(PhB)O}3SiBut] (1) and
(a) pyridine, (b) N,N,N0,N0-tetramethylethylenediamine
4.3.1. Synthesis of [ButSi{O(PhB)O}3SiBut] Æ C5H5N (12)
Compound
1,
[ButSi{O(PhB)O}3SiBut]
(0.11 g,
0.275 mmol) was dissolved in ether (30 ml). While vigor-
ously stirring, pyridine (0.05 g, 6.23 mmol) was added via
micopipette. The reaction mixture was stirred for 16 h.
Removal of ether on a rotary evaporator afforded a colour-
less product. Crystallisation from CH2Cl2–heptane (1:3)
yielded [ButSi{O(PhB)O}3SiBut] Æ C5H5N (12) (0.046 g,
73.4%), m.p. 218–219 °C. Anal. Calc. for C31H38O6B3NSi2:
The structures were refined on F2 [22] to R1 0.055, 0.064,
0.074, 0.043, 0.083 and 0.071 for 3389, 3115, 3338, 6403,
496 and 1589 reflections, respectively, with I > 2r(I) and

2492
G. Ferguson et al. / Polyhedron 26 (2007) 2482–2492
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Organomet. Chem. 526 (1996) 195.
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Reed, J. Chem. Soc., Chem. Commun. (1993) 1816.
[6] L.A. Neville, T.R. Spalding, G. Ferguson, Angew. Chem., Int. Ed. 39
(2000) 3598.
wR2 0.127, 0.193, 0.177, 0.129, 0.155 and 0.238 for all inde-
pendent reflections.
Acknowledgements
The 11B and 29Si NMR spectra were kindly recorded on
a Bruker AM 400 instrument at the University of Leeds by
Prof. J.D. Kennedy. G.F. and S.E.L. thank NSERC Can-
ada and University College Cork for funds for
diffractometers.
[7] A.G. Avent, S.E. Lawrence, M.M. Meehan, T.G. Russell,
T.R. Spalding, Collect. Czech. Chem. Commun. 67 (2002)
1051.
[8] F.J. Feher, T.A. Budzichowski, J.W. Ziller, Inorg. Chem. 31 (1992)
5100.
[9] O. Graalmann, U. Klingebiel, W. Clegg, M. Haase, G.M. Sheldrick,
Z. Anorg. Allg. Chem. 519 (1984) 87.
[10] F.H. Allen, O. Kennard, D.G. Watson, L. Brammer, A.G. Orpen, R.
Taylor, J. Chem. Soc., Perkin Trans. II (1987) S1.
[11] B.J. O’Leary, Ph.D. Thesis, University College Cork, National
University of Ireland, Cork, Ireland, 1998.
[12] D. Murphy, J.P. Sheehan, T.R. Spalding, G. Ferguson, A.J. Lough,
J.F. Gallagher, J. Mater. Chem. 3 (1993) 1275.
[13] B.J. Brisdon, M.F. Mahon, K.C. Molloy, P.J. Scholfield, J. Organo-
met. Chem. 435 (1992) 11.
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3034.
Appendix A. Supplementary material
CCDC 615803, 615804, 615805, 615806, 615807 and
615808 contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplemen-
tary data associated with this article can be found, in the
online version, at doi:10.1016/j.poly.2006.12.045.
[15] G. Ferguson, A.J. Lough, J.P. Sheehan, T.R. Spalding, Acta
Crystallogr., Sect. C 47 (1991) 379.
[16] G. Ferguson, J.F. Gallagher, D. Murphy, J.P. Sheehan, T.R.
Spalding, Polyhedron 12 (1993) 859.
[17] N. Winkhofer, H.W. Roesky, M. Noltemeyer, W.T. Robinson,
Angew. Chem., Int. Ed. 31 (1992) 599.
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